A conventional gate driver circuit used for driving a power switching device of a power converter utilizes semiconductor switching devices to turn on the power switching device and to discharge an input capacitance thereof when the power switching device is turned off. Such a conventional power switching device driver circuit loses approximately twice the energy stored in the device's input capacitance each time the device switches through an on and off cycle. Furthermore, as the operating frequency of the converter increases, power dissipation in the switching devices also increases. However, by operating the power converter at higher frequencies, smaller reactive components can be used, resulting in a smaller power supply. Thus, there is a tradeoff between power supply efficiency and size.
A concurrently filed R. L. Steigerwald U.S. patent application Ser. No. 447,948, now allowed U.S. Pat. No. 4,967,109 discloses and claims a gate driver circuit which reduces gate switching losses by approximately one-half as compared with a conventional driver. In that driver circuit, an inductance is situated in series with the two switching devices of a half-bridge driver, and a Schottky diode is coupled in series between the upper switching device and the gate-drive power supply. During turn-on of the power switching device, the voltage across the power device input capacitance resonates to approximately twice the amplitude of the gate drive power supply. Advantageously, therefore, the gate drive supply voltage is required to be only one-half the desired input capacitance voltage. The only gate switching losses during turn-on are due to the resistances of the nonideal circuit elements. The input capacitance is prevented from discharging to the supply by the Schottky diode. As in conventional drivers, when the power device is turned off, the input capacitance discharges through the lower switching device of the half-bridge. Hence, since turn-on gate losses are substantially zero, the only significant gate switching losses occur during device turn-off so that gate switching losses are reduced from their expected amount by approximately one-half.